The continuing miniaturization of microelectronic devices and the desire to produce faster devices has resulted in a shift toward the use of dielectric materials having a lower dielectric constant (k) than conventional silicon dioxides. In particular there are several advantages associated with using ultra-low k dielectric materials (e.g., a k less than 3) as an insulating layer. Ultra-low insulating layers allow smaller spacing between device features by reducing the extent of crosstalk and capacitive coupling between devices. Using ultra-low k dielectric materials as intra-layer or inter-metal insulating layers can also reduce the requisite drive current and power consumption for microelectronic devices. Moreover device speeds are increased because the RC delay associated with interconnect metal layers and intra-metal dielectric layers is decreased when using ultra-low k insulating layers.
There is growing interest in the use of insulating layers made of porous ultra-low k silicon-based dielectric materials. Insulating layers made of porous ultra-low k silicon-based material retain many of the advantages of conventional silicon oxides, thereby allowing ready integration into existing integrated circuit manufacturing processes. Unfortunately insulating layers made of porous ultra-low k silicon-based dielectric layers are also more susceptible to cracking and fracture than conventional silicon dielectric materials. Consequently integrated circuits containing insulating layers made of porous ultra-low k silicon-based dielectric material can have reduced reliability, or there are reduced manufacturing yields of operative integrated circuits.
Current methods to reduce cracks in porous ultra-low k silicon-based dielectric layers include electron beam or UV curing. Both of these methods are problematic however. Electron beam curing undesirably induces surface damage, increases k, increases thickness non-uniformity and increases moisture absorption. UV curing also undesirably increases k, thickness non-uniformity and moisture absorption, and additional requires long processing times (e.g., 5 to 10 minutes). Moreover, the cost the electron beam or UV curing tool and its maintenance significantly increase manufacturing costs.
Accordingly, what is needed in the art is an insulating layer with improved crack resistance and a method of manufacturing the same that can be easily and inexpensively integrated into existing integrated circuit fabrication processes.